Propeller control



June 24, 1947. w. s. HOOVER PROPELLER CONTROL 2 Sheets-Sheet 1 Filed Marbh 14, 1941 lNVENTORf WalferScotz Hoover BY ATTORNEY.

June 24, 1947. w. s. HOOVER ,PROPELLER CONTROL 2 Sheets-Sheet 2 Filed March 14, 1941 m w I I ATTORNEY halter ScoftHaover W 4 M .F'atented June 24, 1947 UNITED". STATES P TENT orrlca Walter scot z l l otv rffi oifimbec, Canada Application March 14;oS el::3l)N0. 388,392

- Claims.

This invention relates to improvements in con- I trol devices for controllable-pitch constant-speed propellers and has particular reference to an im-- proved control connection between such a prosponse to the governor speed change requirement. f

A still further object resides in the provision oi an improved propeller control of the character indicated which utilizes entirely separate hydraulic systems for the governor and for the propeller pitch changing mechanism and avoids the necessity oi providing an oil transfer bearing on the propeller shaft by utilizing a mechanical connection. between the governor and the propeller.

Other objects and advantages will be more particularly pointed out hereinafter or will be come apparent as the description proceeds.

In the accompanying drawings, in which like reference numerals are used to designate similar pzirts throughout, there is illustrated a suitable mechanical embodiment for the purpose of disclosing the invention. The drawings, however, are for the purpose of illustration only and are not to be taken as limiting or restricting the invention since it will be apparent to those skilled in. the art that various changes in the illustrated embodiment may be resorted to without in any way exceeding the scope ofthe invention.

In the drawings,

Fig. '1 is a somewhat schematic elevational view of a portion of an aircraft engine and governor and. a portion of an aeronautical propeller showing the disposition of a control apparatus, con structed according to the invention, between the governor and the propeller.

Fig. 2 is a longitudinal sectional view of a suitable form of speed responsive governor.

Fig. 3 is a transverse sectional view on the line 3-3 of Fig.2.

Fig. 4 is a transverse sectional view on the line 4-4 of Fig. 2.

Fig. 5 is a transverse sectional view on the line 5-5 of Fig. 2.

Fig. 6 is a, bottom plan view of the governor i1- lustrated in Fig. 2. A

Fig. 7 is a somewhat schematic view of the iming shown in section to better illustrate the con-' 'struction-thereof.

Fig. 8 is a longitudinal sectional view on the line 8-8 of Fig. 7, and

Fig. 9 is a transverse sectional 9-9 of Fig. 8. Referring to the drawings in detaiLthe numeral l0 generally indicates a power plant, such as an internal-combustion engine, from which projects a drive shaft ['2 carrying a. controllablepitch aeronautical propeller, generally indicated at It. While this propeller may be of anyone of several forms well known to the prior art or may be a specially designed propeller, a propeller such as that illustrated in my prior United States Patent No. 2,023385, issued December 10, 1935, for Hydraulic unit for variable pitch propellers, is particularly well adapted to the form of conview on the line trol apparatus constituting the subject matter of the invention. The engine supports and drives a suitable speed responsive governor, generally indicated at l8, which controls a hydraulic servocontrol 122.

motor, generally indicated at 18, connected with the control lever 20 of the'propeller pump cam A suitable form of governor for the purpose of disclosing the invention is particularly illustrated in Figs. 2, 8, 4, 5 and 6. In the governor illustrated, a drive shaft 24 projects through a base or pad 26 and through the portion of the engine upon which the pad 26 is secured to a driving connection with a movable part of the engine. Within the pad 26 there is a hydraulic pump, generally indicated at 28, comprising a gear member 30 mounted on the shaft 24 and a complementary gear member 32 mounted on an axle supported in the pad 26 and the cover plate 3i secured in position on top of the pad and through which the shaft 24 projects into the governor casing 36. At its outer end the shaft 24 carries a pair of flyballs 38 within a governor cap 40 which fiyballs react against a plunger 42 disposed within the tubular upper portion of the shaft 24 and connected through a pin' 44 with an annular slide valve 46 the flanged ends of which cooperate with annular ports- 48 and 50 provided in a valve sleeve 52 mounted in a suitable chamber in the lower portion of the govthe rack 58 may be connected through a rotatable connection 52, inner sleeve '54 and through pin 66 with the movable abutment 68 at the lower end of the spring. This arrangement provides suitable means for changing the speed setting of.

the governor either at the will of the operator or automatically in response to predetermined operating conditions of the vehicle,"such as an air-* In operation one of these ports, for example the port I4, will be closed off by a. suitable plug and the alternative port left open to accommodate the pump to either direction of rotation'of the governor drive. The pump outlet which also includes two alternatively usable ports leads to a pressure chamber 18 connected with a pressure relief valve I8 comprising a piston reciprocably mounted in a bore in the governor casing and urged to closed position by a suitable compression spring 88 theload on which may be adjusted by suitable means such as the screw threaded abut ment 82. The end of the bore may be closed by a suitable plug 83. From the relief valve chamber 84 a channel 85 leads back to the pump inlet so that pressure fluid vented by the relief valve may be recirculated through the pump in a manner well known to the art. The pressure chamber I8 is connected with an annular port 86 located intermediate the length of the valve sleeve 52 and separated from the ports 48 and 58 by annular shoulders on the valve sleeve so that there are three separate annular chambers around the valve sleeve connected with the ports 48, 58 and 88 respectively. The port 86 and the surrounding annular channel are connected only with the pressure chamber I6 while the port 48 and its surrounding annular chamberare con nected with a fluid channel 88 and the port 58 and its surrounding annular channel are connected with a fluid channel 98. The spaces at the opposite ends of the valve piston 48 are connected together by means of suitable channels, as indicated at 92, leading through the space between the interior of the valve piston and a sleeve 94 mounted on the shaft 24 these spaces being connected with the interior of the engine through suitable apertures 88 leading to the interior of the hollow drive shaft 24 to provide a drain for the governor valve.

With this arrangement hydraulic fluid at a substantially constant pressure will be supplied to the intermediate portion of the governor actuated valve by the pump 28 and, when the valve piston 46 is in a lower position incident to an Y 4 I a source oi hydraulic fluid and two outlet lines and a. valve capable of connecting one outlet line with fluid under pressure and the other with drain through the port 58 and, conversely, when 'governor is in a neutral or on-speed condition both ports are blocked off entirely and fluid will not flow into or out of either of the lines 88 and This arrangement provides a governor having drain and of reversing this connection in response to changes between overspeed and underspeed conditions of the governor driving engine, and of blocking off both lines when the engine is operating at an "on-speed condition.

Any suitable type of propeller having a lever or mechanism that may be moved to change the propeller pitch may be utilized. For purposes of illustration the propeller disclosed in my United States Patent No. 2,023,785, has been selected. The propeller, as described in greater detail in my above-mentioned prior United States Patent No. 2,023,785, comprises a hub I82 which supports 'a plurality of blades, as indicated at I84 and I88 in Fig. 1, for pitch changing movements about their longitudinal axes. Within the hub there is a suitable fluid motor I88, which may be a vane type motor, as is particularly described and illustrated in my United States Patent No. 2,023,785, referred to above, and this motor may be connected to the propeller blades by suitable means such as bevel gears for rotating the blades in pitch changing directions upon movement of the movable portions of the vane motor. Two pump units, as indicated at H8 and H2, are carried by the propeller hub I82 and connected through separate channels, III and H6, with opposite sides of the vane motor in such a manner that when one of the pumps is operated the fluid pressure produced by said one Pump will cause the vane motor to rotatein one direction and, when the other pump is operated, the vane motor will be rotated in the opposite direction. By this method of operating the pumps only one pump is operated at a time permitting the alternative pump to remain idle and allowing fluid from the side of the fluid motor connected with the idle pump to drain through a suitable means, to the intake of the operating pump. This method provides for a rapid and positive movement of the propeller blades in either pitch changingdirection.

The pumps H8 and H2 rotate with the propeller I4 and are operated by respective adjustable cams H8 and I28. shown in Figs. 7 and 8, the cams I I8 and I28 are formed on the ends of respective cylindrical members I22 and I24 which are telescopically associated and rotatably mounted on a fixed bearing sleeve I 26 which is eccentric-of the axis of rotation of the shaft I2 by the same amount as the eccentricity of the respectivecams H8 and I28 so that when the sleeves I22 and I24 occupy a predetermined angular position, hereinafter called a neutral position, relative to the fixed sleeve I28 the. peripheries of the cams H8 and I28 will be concentric with the axis of rotation of the shaft I2 and the pumps H8 and H2 will move around the cams without being operated. The movable sleeves are resiliently urged to this neutral angular position by respective spiral spring members I28 and III: which have one end fast in the member I28 and other end fast in the sleeves I22 and I24 respectively and arranged to move the sleeves around the sleeve I28 until the respective limit stopmembers I21 and I3I reach the ends of slots provided therefor in the fixed bearing sleeve I28 and thereby prevent movement of the sleeves away from their neutral position in predetermined directions. The control arm 28 has an annular portion I32 which surrounds the outer movable sleeve I22 and has .lost motion connections in the form of As is particularly blocking both the lines and III.

the respective pins I04 and III with the sleeves I22 and I24. As is particularly shown in Pig. 0, ii the arm be given a right hand or clockwise movement the inner sleeve I24 will be'rotated in the same direction away from its neutral position but the outer sleeve I22 will not be moved because of the space between the pins and the ends of the slots in the member I22 through which the pins project. However, ii

' the arm be given aleft hand or counterclockwise movement the sleeve I22 will be moved in the same direction away from its neutral posiits neu- I00 to attain the pitch changing movement desired.

Movement of the control arm 20 is effected by the servo-motor I0 under the control of the governor I5. This servo-motor comprises a cylinder I30 to one end of which is "connected the governor outlet line 98 and to the other end of which is connected the governor outlet line I00. Within the cylinder there is a piston I40 carried upon a piston rod I42 which projects from one end oijthe cylinder to a"pivotal connection 0 v in] to the'oppcsite end through the channel I00 andthemllellerpitchwillthenbemaintlined at the angle at which it regulated the engine speed to the governorrequirement, since, with the piston I40 in its neutral position. both of the pitch changing pumps III and H2 will be rendered inoperative and flow of hydraulic fluid to and from the pitch changing motor willbe blocked. Whenever the flow through. the governor ports is reduced to a point where his less than the flow through the channel I50 the pis- -ton I40 will tend to move to its neutral position.

I44 with thefree end of the control arm 20,

this connection being provided with sufilcient freedom lengthwise of the control arm to permit free angular movements of the arm upon reciprocation of the piston-I in the cylinder I38. Compression springs I40 and I40 are disposed between the piston and the opposite ends of the cylinder to resiliently urge the piston to its central or neutral position, as illustrated, in which the control arm 20 is brought to its neutral position and the propeller is maintained against pitch change. A channel I50 leads through the piston and opens at opposite sides thereof and within this channel is a double acting ball check valve I52 urged to its central or neutral position, in which it does not close the passage, by'balanced opposed compression springs I54 and I56. The springs I54 and I50 are sumciently still so that the check valve Il2tis not moved to valve closing position until one of the springs I40 or I40 has reached its solid or bottomed condition and the greater pressure dif- -ference between the two sides of the piston I40 causes an increased flow past ball I 52 thus moving the ball I52 to valve closing position. With this arrangement when the governor-actuated valve, in response to a speed change re- By properly dimensioning the governor valve ports and the channel III a return of the'piston I40 to its neutral position can be' initiated slightly below the governor valve cuts-oil so that the return 0! the piston to its neutral position can be timed to exactly coincide with .the propeller pitch changing mechanism or hunting of this mechanism in the attempt to attain the speed required by the governor.

- In some instances, as when an engine is first started, it may-require a considerable time interval for the engine to come up to the speed for which the governor is set. In such a case the governor would operate the governor control valve in a manner to bring the propeller to its positive low pitch setting and retain itin thatposition until the engine speed approached that of the governor speed setting. In such a case if the channel 150 were left open there would be a considerable flow of oil through the servo-motor I0 during this time interval. With the inclusion of the check valve I52. however, as soon as the piston I40 has moved to its limiting position, continued flow of oil into the pressure side of the cylinder I38 will. attempt to force an increased quantity of oil past the ball I52 and move the ball I52 to close oil this channel and thereby prevent a further bleeding of pressure fluid from the pressure line leading from the governor to the drain line leading from the servo-motor back to the governor. This check valve will, therefore, prevent an excessive bleeding of engine lubricating fluid during the engine warm-up period and may be useful on other occasions to prevent a.

flow of hydraulic fluid from the governor source oi fluid pressure back to drain. As soon as the engine has reached the speed required by the governor, the governor actuated valve will cut-- oil the supply 01' pressure fluid to the servo-motor and a very slight leakage of the pressure fluid either through this valve or past the piston or through the governor will relieve-the pressure on the valve ball I52 caused by the trapped oil. As the actionof the springs I46 or I48 on the trapped oil is not suflicient to hold the ball I52 on its seat a slight leak will reduce the pressure .suf-

ficiently to permit this ball to assume its neutral position whereuponthe centering springs I40 and trol arm 20 and actuate one of the pumps "0 or II2 to, change the propeller pitch. As soon as the change in propeller pitch has created the required speed change the governor valve will be moved to its neutral or cut-oi! position pressedone of the springs I40 or I40 willthen act to move the piston I40 back to its neutral position, fluid from one end of the cylinder flow- The com-- I48 will return the piston I40 to its neutral posic Having now described the invention so that others skilled in the art may clearly understand the same, what it is desired tosecure by Letters support and having another portion carried by said propeller, and a servo-motor mounted on 'said support and actuated by fluid controlled by said governor and operatively connected with 'said one portion of said mechanical device, said servomotor comprising a cylinder, 9. piston in said cylinder movable in opposite directions from a neutral'position, means resiliently urging said piston toward said neutral position, and a restricted, normally open, fluid passage from one side of said piston to the other and means for closing said passage.

2. Mechanism for operatively connecting a speed-responsive governor mounted on a fixed support with a relatively rotatable controllablepitch propeller comprising, a mechanical device for controlling pitch changing movements of said propeller and having one portion mounted on said support and having another portion carriedby said propeller, and a servo-motor mounted on said support and actuated by fluid controlled by said governor and operatively connected with said one portion of said mechanical device, said servotoward said neutral position, and a restricted fluid passage from one side of said piston to the other and a check valve in said passage resiliently held in valve open position but movable to a closed position to prevent flow of oil above a predetermined rate from one side of said piston to the other.

3. Mechanism for operatively connecting a speed-responsive governor mounted on a fixed support with a relatively rotatable controllablepitch propeller comprising, a mechanical device for controlling pitch changing movements of said propeller and having one portion mounted on said support and having another portion carried by said propeller, and a servo-motor mounted on said support and actuated by fluid controlled by said governor. and operatively connected with said one portion of said mechanical device, said mechanical device comprising a pair oi pumps mounted to rotate with the propeller, a pair of pump actuating cam members mounted on a including'a piston and cylinder construction connected with said stationary part for'positioning said stationary part and controlling the actuation of said pitch changing mechanism and having a neutral position in which said pitch changing mechanismis maintained against substantial movement, resilient means continuously urging said connection toward said neutral position, said connection being moved away from said neutral position by operation of said governor, and means, including av by-pass from ,one side of the piston to the other and pressure actuated means controlling said by-pass, operable by pressure on one, side of said piston to close said bypass and operable upon a reduction'in said pressure to open said by-pass to permit a return of said connection'to said neutral position by said resilient means.

5. Mechanism for operatively connecting a speed-responsive governor mounted on a fixed support with a relatively rotatable controllablepitch propeller comprising, a. mechanical devive for controlling pitch changing movements of said propeller and having one portion mounted on said support and having another-portion carried by said propeller, and a servo-motor mounted on said support and actuated by fluid controlled by said governor and operatively connected with said one portion of said mechanical device, said servomotor comprising a chamber and a partition dividing said chamber and movable in opposite directions from a neutral position, means resiliently urging said partition toward said neutral position,

fixed bearing eccentric to the axis of rotation of said propeller by an amount equal to the eccentricity of said cams, means comprising a single. lever for selectively moving said cams one at a time away from a position of concentricity with said axis of rotation, means connecting said single lever with both of said cams, means connecting said single lever with said servo-motor and means resiliently urging both of said cams toward said position of concentricity.

4. In a propeller pitch control a paratus including a speed responsive governor mounted on a stationary support and a pitch changing mechanism having a stationary part and a part carried by said propeller cooperating with said stationary part and arranged so that said pitch changing mechanism is actuatable by propeller rotation, a connection between said governor and said pitch changing mechanism for controlling said pitch changing mechanism, said connection and a restricted fluid passage from one side of said partition to the other and a check valve in said passage resiliently held in valve open position but movable to a closed position to prevent flow of fluid above a predetermined rate from one side of the partition to the other.

- WALTER SCOTT HOOVER.

REFERENCES CITED.

The following references-are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,723,617 Hole-Shaw et al. Aug. 6, 1929 1,972,486 Hoover Sept. 4, 1934 2,023,785. Hoover Dec. 10, 1935 2,055,396 Yoxall Sept. 22, 1936 2,114,076 Golz- Apr. 12, 1938 2,115,121 Phillips Apr. 26, 1938 2,129,828 Dunn Sept, 13, 1938 2,166,423 Clark July 18, 1939 2,248,789 Setterblade July 8, 1941 2,210,009 Ruths et al. Aug. 6, 1940 2,007,417 Aivaz July 9, 1935 2,229,058 Dicks Jan. 21, 1941 2,225,408 Berliner Dec. 17, 1940 2,284,154 Lampton et al. May 26, 1942 2,184,143 Hoover Dec. 19, 1939 1,959,889 Wunsch May 22, 1934 1,875,598 Heath Sept. 6, 1932 1,963,664 Lambert 'June 19,1934

FOREIGN PATENTS Number Country Date 499,634 Great Britain 7 Jan. 26, 1939 797,873 France Feb. 24, 1936 802,046 France May 30, 1936 134,258 Great Britain Oct. 30, 1919 434,567 Great Britain Sept. 4, 1935 635,992 Germany Sept. 30, 1936 

